The main objective of this proposed research is to determine the role of a newly described cholera toxin crossreactive factor in the pathogenesis of Aeromonas hydrophila mediated diseases. The virulence factors associated with A. hydrophila reported in the literature have not been clearly defined. A. hydrophila, a close relative to Vibrio cholera, has recently been recognized as an important human pathogen. This organism is capable of causing a variety of diseases, including acute bacterial diarrhea, septecemia, meningitis, endocarditis, corneal ulcers, peritonitis, and wound infections. Fatalities have occurred even in healthy, immunologically competent persons. The symptoms of disease produced during Aromonas infections are in part related to the elaboration of toxic extracellular products. We have discovered that A. hydrophila strain SSU, grown in Casamino acid-yeast extract (CYE) medium, can produce high levels of a toxic extracellular product that crossreacts with cholera enterotoxin as determined by the enzyme-linked immunosorbent assay (ELISA). We have termed this extracellular product "cholera toxin crossreactive factor" until further characterization is accomplished. The same culture filtrate containing this cholera toxin crossreactive factor causes damage to Vero (green monkey kidney) cell membranes and lysis of rabbit red blood cells. When this filtrate was injected intravenously into mice, lethal effects are exhibited. We will purify and characterize this cholera toxin crossreactive factor antigenically, biologically, and biochemically. Our laboratory will investigate the mechanism of action of this extracellular factor. In addition, the type of genetic information that codes for the synthesis of this virulence factor will be explored. Physicochemical studies of this cholera toxin crossreactive factor will be initiated. This cholera toxin crossreactive extracellular product may be the result of Aeromonas exterotoxin and cytotoxin combining in the CYE medium to make a larger complex molecule possessing both enterotoxic and cytotoxic activities. Experiments are described in this proposal to investigate this hypothesis. The proposed research involving this potential virulence factor should improve our understanding of the mechanisms of Aeromonas hydrophila infections.